import math

def main():
    X1, Y1, X2, Y2 = map(float, input().split())

    dist = math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2)
    print(dist)

main() import math math def main():
    X1, Y1, X2, Y2 = map(float, input().split())

    dist = math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2)
    print(dist) main X1, Y1, X2, Y2 = map(float, input().split()) X1 map(float, input().split()) map float input().split() ().split () input split Y1 X2 Y2 dist = math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2) dist math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2) math.sqrt math sqrt (X2 - X1) ** 2 + (Y2 - Y1) ** 2 (X2 - X1) ** 2 X2 - X1 X2 X1 2 (Y2 - Y1) ** 2 Y2 - Y1 Y2 Y1 2 print(dist) print dist main() main def main():
    X1, Y1, X2, Y2 = map(float, input().split())

    dist = math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2)
    print(dist) def main():
    X1, Y1, X2, Y2 = map(float, input().split())

    dist = math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2)
    print(dist) main
import math

def main():
    X1, Y1, X2, Y2 = map(float, input().split())

    dist = math.sqrt((X2 - X1) ** 2 + (Y2 - Y1) ** 2)
    print(dist)

main()